I think it should be because diplomats is the representative of a nation and negotiating with other nations could be more easier if we're already friendly with the diplomat. Also the way we treat their diplomat is also the way of how we treat the nation he/she representing and it would add a good standing in the global status if we are respecting the diplomats.
Catherine the Great, was an empress of Russia who ruled from 1762-1796,
C. Mansa Musa was a baller and he built up Africa by being the richest person in human history
El Greco slipped his own portait into one of his paintings.
